In the field of noise and flash reduction of firearms there has presented quite many different constructions and devices for the same purpose i.e. to dampen the noise and flash caused by the rapid burning of propellants when the firearm is fired. As the benefits of this reduction are quite obvious, the noise of undamped firearm may exceed 130 dB, even 160 dB, and can be harmful for firearm users or anyone nearby and disturb large surrounding areas, for example by a hunting area or by a shooting range. It is also preferred to be avoided or at least minimized in military applications where the sound of the firing immediately attracts the attention of parties concerned. The better the suppressor is in terms of noise reduction and if combined to easy or simple manufacturability, the better the suppressor is in terms of commercial interest.
A firearm bullet or in general a projectile, is rapidly accelerated at firing to an initial velocity of 300 to 1100 m/s depending the type of the firearm. The initial velocity means here the velocity of the projectile when exiting the barrel or corresponding part of a firearm. This means that the initial velocity may be within range on about 0.8 to 3.3 Mach (where 1 Mach is the speed of the sound when the medium is normal atmospheric air in about normal temperature and pressure (ntp)). Thus the flow dynamics range of concern may vary from slightly subsonic to highly supersonic flows.
In case of supersonic noise dampening, the suppressor is not capable of reducing the noise originating from the projectile breaking the sound barrier during the flight to a destination. Thus the aim of the suppressor is to reduce as much as possible the noise generated by the phase when the bullet is no longer in front of that high pressure propellant gas and the pressure is rapidly normalizing to an atmospheric pressure, the burning propellant is exiting the barrel and when the propellant residuals are burning outside the barrel.
From the state of the art various different constructions are known, but the science behind the theory is still in some extent unknown. One publication is EP 2 191 223 B1, which presents one theory and a firearm suppressor applying that theory. The construction shows a suppressor comprising a number of mixer/ejector type nozzles located within the suppressor housing and that the suppressor housing is provided with vent holes for providing ambient air to be mixed with propellant gases at the nozzles.
From the state of the art it is also known EP 0 660 915 B1, which presents a firearm suppressor that can be adapted for use with a wide range of ammunition types by virtue of the following features: an adapter designed to be attached to the mouth of the barrel; an end-piece forming the mouth of the silencer, with an aperture designed to allow the projectile to pass out; a central element, located between the adapter and the end-piece, with a number of compartments disposed one behind the other in a straight line, each compartment having an aperture designed to allow the projectile to pass through; each compartment being attached in modular fashion to the next compartment and the outer walls of the series of compartments forming the outer wall of the silencer.
From the state of the art is WO00/57122, which presents a suppressor having deflector cones for guiding the gas flow. The deflector cones have holes to direct the combustion gases outside the cone.